For convenience purposes, it is well known to provide garage doors which utilize a motor to provide opening and closing movements of the door. Motors may also be coupled with other types of movable barriers such as gates, windows, retractable overhangs and the like. An operator is employed to control the motor and related functions with respect to the door. The operator receives command signals for the purpose of opening and closing the door from a wireless remote, from a wired or wireless wall station or other similar device. It is also known to provide safety devices that are connected to the operator for the purpose of detecting an obstruction so that the operator may then take corrective action with the motor to avoid entrapment of the obstruction.
How safety devices are used with a door operator system have evolved from the days of no uniform standard to the currently applied government regulations as embodied in Underwriters Laboratories Standard 325. UL Standard 325 encompasses safety standards for a variety of movable barriers such as gates, draperies, louvers, windows and doors. The standard specifically covers vehicular gate or door operators intended for use with garages and/or parking areas. Such devices require a primary safety system and a secondary safety system which are independent of each other. Primary entrapment systems sense the operator motor's current draw, or motor speed and take the appropriate corrective action if the monitored value is exceeded. Primary systems must be internal within the operator head. Secondary entrapment systems are typically external from the operator head and may include a non-contact or contact type sensor. But, secondary systems may also be internal to the operator head as long as they are independent of the primary system.
One of the more widely used non-contact devices is a photo-electric eye which projects a light beam across the door's travel path. If the light beam is interrupted during closure of the door, the operator stops and reverses the travel of the door. Contact type safety devices such as an edge-sensitive pressure switch, which is attached to the bottom edge of the door and runs the complete width of the door, may also be used. Other contact safety devices directly monitor the operating characteristics of the driving motor to determine whether an obstruction is present. Typically, shaft speed of the motor is monitored by projecting an infrared light through an interrupter wheel. Alternatively, Hall effect switches or tachometers can be used to monitor shaft speed. Or, the motor current could be monitored such that when an excessive amount of current is drawn by the motor—which indicates that the motor is working harder than normal—it is presumed that an obstruction has been encountered. It is also known to monitor door speed with a sliding potentiometer, wherein a rate of change is equated to the speed of the door and wherein unexpected slowing of the door triggers corrective action by the operator. The secondary entrapment requirement may also be met by providing an operator that is capable of receiving continuous pressure on an actuating device that is in the line of sight of the door and maintains the opening or closing motion until the respective limit position is reached. Regardless of how the safety devices work, their purpose is to ensure that individuals, especially children, are not entrapped by a closing door. Opening forces of the door are also monitored to preclude damage to the operating system for instances where an object or individual is caught upon a door panel as the door moves upwardly.
Prior art devices have either user access adjustment settings or internal automatic predetermined settings to set the force the operator-driven motor can exert on the barrier or door. User access settings can be set by cycling the door and testing the amount of force the door is exerting before it reverses. This repeated cycling may take some time and effort to adjust the setting properly for each weight and size door a particular type of operator is associated with. Without having an indicator to indicate when the door force setting is properly adjusted, many times the force is adjusted too high, for a number of reasons. For example, the settings may be adjusted too high to overcome environmental changes; or because of wear and changes to components such as the door, hinges between the door panels, the spring, the door track and so on. The setting may also be adjusted by untrained personnel and if no warranty maintenance is ever performed, the setting will likely be left at an exceedingly high and dangerous value. In any event, the door operates without a problem until something becomes entrapped under the door. As a result, when the unnecessarily high force is used, the entrapped object or the door, or both, are damaged. The automatic internal force adjustment solves these problems, but the units that incorporate this type of technology may not work with all weights and sizes of doors. Some attempts at solving the aforementioned problem are disclosed in the following U.S. Patents.
U.S. Pat. No. 4,597,428 to Iha discloses aworm drive with a cable and twin drums and helical gears which provide positive drive in either direction and ensures positive cable take-up and supply spool synchronization. Positive position relationship is ensured between the trolley and the operator head, and the ends of the cable are pre-assembled and anchored to the drive reels which allows easy assembly and disassembly. The cable is oriented in the vertical plane which allows the point of the cable latch to be in the same load/force plane and effectively minimizes the rail bowing under severe load conditions. The tubular rail can be broken into disassembled parts and can be easily and quickly reassembled for installation and a novel tension adjustment for the cables assures that the tension of the cable can be quickly and easily adjusted during installation. The up and down limits can be easily adjusted and the up and down force adjustments can be accurately and easily adjusted and merely require the setting of potentiometers which provides a positive and accurate way of adjusting the up and down force limits. But this configuration does not provide any type of user feedback. As such, the user is never quite sure if just the minimum force required to close the barrier is being used.
U.S. Pat. Nos. 5,929,580 and 6,326,751 to Mullet, et al. disclose an internal entrapment system for a garage door operator, comprising a motor for transferring a garage door between first and second positions, a pulse counter for detecting a speed of the garage door during transfer between first and second positions, a potentiometer for determining a plurality of positional locations of the garage door during transfer between first and second positions separate from the pulse counter, and a control circuit for calculating a motor torque value from the speed for each of the plurality of positional locations to compare with a plurality of door profile data points. The control circuit takes corrective action if the difference between the motor torque value for each of the plurality of positional locations and the plurality of door profile data points exceeds a predetermined threshold. And the control circuit updates the plurality of door profile data points to the motor torque values for each respective plurality of positional locations if the predetermined threshold is not exceeded. In another embodiment both speed and position are detected by a slider element which is connected to the control circuit. A closed loop lift cable system may be employed for use with the internal entrapment system. The system utilizes a lift cable connected between a bottom section of the door and a drum mechanism and an upper cable connected between a top section of the door and the drum mechanism. A tension device ensures that the door and cables act as one and thus allow closed loop control of the door. One of the objects of this embodiment is to provide an internal entrapment system to monitor door speed and applied force as the door travels in the opening and closing directions, wherein if the door encounters an obstacle during opening and closing, the door speed and applied force will change. Another object of the present invention is to stop and reverse or just stop travel of the door if predetermined thresholds in door speed and applied force are not met. Still another object of the present invention is to generate door profile data during an initial door open and close cycle and whereupon the door profile data and predetermined thresholds are updated after each cycle. The unit monitors the operational characteristics of the operator and determines the proper force adjustment in both the up and down directions compared to predetermine thresholds and will not allow user adjustment. The system requires many sensors and an extensive software program to function. But, this system is deficient in that it does not provide for any user feedback when setting the down force value used by the controller.
U.S. Pat. No. 5,278,480 to Murray discloses a garage door operator with a micro-computer based control which is programmed to measure door position from a full open position by counting motor revolutions and which determines motor speed and deceleration for each revolution. The program learns the open and close position limits and force sensitivity limits for up and down operation with supposedly minimal user input. The patent discloses that during normal door operation the closed limit and sensitivity limits are adaptively adjusted to accommodate changes and conditions. The lowest up and down motor speeds in each operation are stored for comparison with motor speeds in the next like operation for obstruction detection. For a more sensitive obstruction detection during closing, the motor speed is mapped for each revolution for the last several inches of closing. Although effective in its stated purpose, it is believed that an excessive amount of force may still be applied to an obstruction inasmuch as the force applied may still be more than required to actually close the door. Moreover, no user feedback mechanism is provided such that the user can determine what the minimum force setting is during a programming mode.